In rotary piston mechanisms of various types having multi-lobe housing cavities, such as those disclosed in the U.S. patents to Wankel et al, U.S. Pat. No. 2,988,065 dated June 13, 1961; Nubling U.S. Pat. No. 2,866,417 dated Dec. 30, 1958; Kraic et al, U.S. Pat. No. 3,323,498 dated June 6, 1967; Kolbe et al, U.S. Pat. No. 3,671,154 dated June 20, 1972; Batten, U.S. Pat. No. 2,873,250 dated Mar. 25, 1975; Huf, U.S. Pat. No. 3,797,974 dated Mar. 19, 1974 and Huf, U.S. Pat. No. 3,923,430 dated Dec. 2, 1975, the working chambers formed between the rotor and the housing cavity walls are isolated from each other and surrounding areas by a sealing grid assembly comprising side wall sealing means and apex seals carried by the rotor or non-rotating seal elements disposed at the junctions of the housing cavity lobes. Heretofore, it was not considered possible to provide optimum volumetric efficiency by employing both apex seals and non-rotating seal elements (hereinafter referred to as "waist seals") because of the rapid failure of the seals due to the accumulative effects of repeated impacts between the apex seals and the non-rotating seal elements. While counterweighted apex seals which function to retract at the lobe junctures are known and disclosed in various U.S. patents, such as the patent to Jones, U.S. Pat. No. 3,456,626 dated July 22, 1969; Jones U.S. Pat. No. 3,482,551 dated Dec. 9, 1969 and Kumar, U.S. Pat. No. 3,909,013 dated Sept. 30, 1975, the use of such apex seals in combination with waist seals would not eliminate the impact problem without an appreciable increase in leakage or blow-by at the apex seals. The prior art teaching, as exemplified in the U.S. patent to Batten, U.S. Pat. No. 3,873,250 and the French patent to Planche, U.S. Pat. No. 590,085 dated June 10, 1925, which disclose the pressurization of the apex seals to bias them outwardly of the grooves, even at the lobe junctures, obviously do not provide a solution to the impact problem. One solution to the problem is disclosed in the co-pending U.S. patent application, Ser. No. 689,184, filed May 24, 1976, now U.S. Pat. No. 4,043,714, which discloses fluid pressure actuated "nose" or apex seals. These seals are relatively complex and unsuited for inexpensive compressors or other types of rotary mechanisms.
Another object of the present invention is to provide an improved rotor for a rotary piston mechanism of the multi-lobe type which simplifies the sealing grip system and thereby renders the entire mechanism relatively inexpensive.
A further object is to provide for a rotary piston mechanism of the multi-lobe type, an improved rotor which maintains continuous sealing contact with the waist seals and, at its apex portions, with the inner peripheral surface of the housing cavity as the rotor planetates.
A feature of this invention is to provide the improved rotor for a rotary piston mechanism of the multi-lobe type, having waist seals, with an endless, flexible band embracing the periphery of the rotor which band is capable of automatic flexure for the maintenance of engagement, at various points, with the peripheral wall of the cavity as the rotor planetates with the housing cavity while avoiding impacts with the waist seals.